Electrolytic refining of tin.



R. L. WHITEHEAD.

ELECTROLYTIC REFINING 0F TIN. APPLICATION FILED MAY 4. 191's.

Patehted Oct. 26, 1915.

2 SHEETS-SHEET l.

R. L. WHITEHEAD.

ELECTROLYTIC REFINING 0F TIN. APPLICATION FILED MAY-1. ms.

Patented Oct; 26, 1915.

2 SHEETSQSHEET 2;

44 WWW;

ROBERT Il- WHITEHEAD, F PERTH AMBOY, NEW J ERSEY, ASSIGNOR TO AMERICAN SIZIELTING & REFINING COMPANY, 015 MAURER, NEW JERSEY, A CORPORATION OF NEW JERSEY.

menace.

I ELECTROLYTIC REFINING OF TIN.

Patented (let. 2%, IHl'll5.

' n ncationmeanay t, 1915. Serial No. 2am.

Y To all whom it may concern:

Be it known that I, ROBERT L. WHITEHEAD,

a citizen of the. United States, residing at Perth Amboy, county of Middlesex, State of New Jersey,,have invented certain new and useful Improvements in Electrolytic Refim ing of 'Iin; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. I

My invention relates to certain new and useful improvements in the production of electrolytically refined tin from impure tin cast in the form of anodes.

In the practiceof the invention, I first produce from the impure tin itself, an' elec:- trolyte of such a character that it wlll- 1nsure the continued maintenance of the electrolytic deposition of the tin during the refining operation and which will itself be devoid of lead, which is an impurity usually present in the tin to be refined. So also,

after the electrolyte has been initially produced, I maintain its purity, during the refining operation, by still further continuing to exclude the entrance of lead from the tin anodes into the electrolyte. The tin anodes usually contain gold, silver, or other values,

in addition to lead, and I find that all of these adhere for the most part, as slimes, to the anodes, and may be removed therewith at the termination of-the electrolytic treatment; or, in part, they fall"to thebottom of the electrolytic tank, from which they may be withdrawn, when occasion requires.

'Ihe expedient that I employ for preventing the entry of lead into solution in the electrolyte'from the impure tin anodes is to employ in the electrolyte, during its preliminary formation and-subsequently during the deposition of the tin therefrom upon the cathodes an agent which'will convert the lead into .a compound insoluble in the electrolyte. The agent that I prefer to employ for the purpose is sulfuric acid,.-which serves to convert the lead into' lead sulfate, insoluble in the electrolyte which I employ, as will hereinafter more fully appear.

In the accompanying drawings, I have illustrated a form of apparatus suitable for the practice of the invention.

1 Figure 1 represents a top plan view of the apparatus; Fig. 2 represents a sectional view of sald apparatus on a plane indicated by odes c,+d indicating the location of the bus- ,cated the series of impure tin anodes Z) alternatmg with a corresponding series of cathbar withwhich the primary series of the anodes makes connection.

I employ as the electrolyte, a solution obtained by dissolving metallic tin in hydrofluosilicic acid: To obtain this electrolyte, I may conveniently make use of the apparatus shown in the drawings, wherein the anodes b are of the impure tin to be refined, and

wherein thecathodes c are contained within cells e of porous earthenware or th like Supported from the bottom-of the vat upon glass insulator blocks f. To maintain the porous cells in position upon the glass insulator blocks it will be convenient, as shown, to provide the cathode bars 9 with clips h ofsheet metal which prevent the cups from shifting their position. So also, clips 6 serve to support the cathode sheets from the cath ode bars. I

In preparing the electrolyte from the impure tin anodes, I may employ cathodes either of tin, copper,.lead, or other-.appropriate metal. In the main body portion of the vats A and also in the porous cells 6, I employ a 20% solution of hydrofluosilicic acidycontaining' 1% by weight of sulfuric acid. An electric current of suitable voltage and amperage is then applied until, upon testing, the solution has taken up 6%" by weight of tin whereupon the passage of the current is then discontinued. During this preliminary formation of the electrolyte, the

sulfuric acid containedin the solution pour biries with the lead which would otherwise go into solution in the electrolyte and converts it into lead sulfate which is lIlSOlllble therein. The electrolyte thus produced con sists of tin dissolved in hydrofluosilicic acid, and has been formed from the impure tin anodes without bringing any of the lead into 5 solution. The electrolyte is therefore adapted to deposit pure tin upon cathodes, provided that it is further protected during the depositing operation from contamination by lead.

After the formation of the electrolyte, the porous cells 0. are removed, and cathodes, preferably of tin are suspended freely in the electrolytic vats to receive the deposition of the tin. The removal of the porous cells permits the lowering of the voltage of the current to one-half a volt in lieu of the four to five volts employed during the formation of the eletrolyte. The electric depositing current being then applied to the apparatus, the tin in a pure state is deposited upon the cathodes from the impure anodes, and the purity of the electrolyte is insured by maintaining insolution therein a quantity of sulfuric acid appropriate to the conversion of the lead of the progressively dissolving anodes into lead sulfate. As hereinbefore noted, the lead sulfate and the other values contained in the anodes adhere for the most part to the anodes, as slimes,very little, if any, of these constituents falling ofi into the vats. This isa feature of importance in the operationfor the reason that at the termination of the operation, these slimes can be raised out of the solution because of their adhesion to the practically exhausted anodes, so that the annoying inconvenience of removing slime deposits from the bottom of the vats is correspondinglydecreased.

What I claim is:

1. In the electrolytic refining of impure tln containing lead, the method of producing an appropriate electrolyte for the refinmg operation, which consists in passing an electric current of suitable voltage and amperage from the impure tin as an anodeto a cathode through an electrolyte which is a solvent of tin and lead, and protecting the electrolyte from contamination by lead, by incorporating with the electrolyte an agent wh ch will combine with the lead to form an insoluble compound; substantially as de scribed. 4

2. In the electrolytic refining of impure tin containing ,lead, the method of producing an appropriate electrolyte for the refining operation, which consists in passing an electrolytlc current of suitable voltage and amperage from the impure tin as an anode to a cathode through a solution of hydrofluosilicic acid containing an agent which will combine with the lead to form an insoluble compound; substantially as described.

3. In the electrolytic refining of impure I tin containing lead, the method of production of the tin deposited from the impure tin anode upon the cathode, which consists in employing an electrolyte which is a solvent of tin and lead, and incorporating in the electrolyte a protective agent sufiicient to convert the lead contained in the dis solving tin anode into a compound insoluble in the electrolyte; substantially as described.

5. In the electrolytic refining of impure tin, the method of preventing contamination of the tin deposited from the impure tin anode upon the cathode, which consists in employing as the electrolyte a solution of tin in hydrofluosilicic acid together with a protective agent sutficient to convert thelead contained in the dissolving tin anode into a compound insoluble in the electrolyte; substantially as described.

6. In the electrolytic refining of impure tin, the method of preventing contamination of the tin deposited from the impure.tin anode upon the cathode, which consists in employing as the electrolyte a solution of tin in hydrofluosilicic acid together with a quantity of sulfuric acid suflicient to convert the lead of the dissolving anode into lead sulfate; substantially as described.

7. The rocess of producing an appropriate electro yte for the refining of impure tin, which comprises passing an electrolytic ourrent of suitable voltage and amperage from a tin anode to a cathode through a solvent adapted to take the tin into solution on passage of the current, and interposing a porous diaphragm between the anode andcathode during the process; substantia lly as-described. v p

8. The process of producing an appropriate electrolyte for the refining of impure tin, which comprises passing an electrolytic current of suitable voltage and amperage from a; tin anode to a cathode through a solution of hydrofluosilicic acid, and interposmg a porous diaphragm between the anode and cathode during the process.

9. An electrolyte for the deposition of tin" uwvgaeo solved from the anode and deposited on the cathode without contamination with substantially as described.

10. An electrolyte for the deposition of tin free from lead, comprising an electrolytic solution of tin in hydrofluosilicic acid containing a small amount of sulfuric acid; whereby, upon the passage of a current;

lead;

therethrou h from an impure tin anode containing lea to a cathode, the tin will be disre solved from the anode and deposited on the cathode Without contamination with lead; substantially as described.

lln testimony whereof I afix my signature.

ROBERT L. WHITEHEAD. 

